This invention relates to the incubation of blood samples and, particularly, to an improved incubation device for maintaining blood samples at constant temperature for a predetermined period of time in preparation for blood cross-matching, enzyme reactions, colorimetric determinations and like routine blood sampling procedures. Among the typical traditional techniques for incubating blood samples has been simply to immerse the test tube or cuvet in a temperature controlled water bath. Although the water bath technique provides accurate control over the temperature of the blood sample, it has presented a number of inconveniences and difficulties which have led to the use of dry heating techniques. Perhaps among the more inconvenient features of the water bath technique is that when the test tube is withdrawn from the bath, water film and/or droplets on the test tube may interfere with subsequent optical tests on the blood sample. It is necessary for technicians to wipe the test tubes dry, and this can become quite a time consuming procedure, particularly in those environments where large masses of blood samples are being tested at the same time. In general, the water baths tend to be somewhat messy.
In order to avoid these difficulties, there has been a trend toward the use of "dry bath" techniques which have, in large part, replaced the traditional water bath for most routine blood testing applications. Typically, the dry baths consist of a heated block having drilled holes receptive to the test tubes. This technique provides other difficulties. For example, it is virtually impossible to assure full and intimate heat transfer contact between the holes in the heater block and the test tubes. Rather, the test tube tends to contact the heater at a number of points, which tends to develop hot spots. Much of the surface of the test tube is spaced from the surface of the heater block by a thin layer of air which accentuates the undesirable localized heating tendency. Often, the dry devices are operated at too hot a temperature in order to compensate for the non-uniform heat transfer effect. This can lead to short life for the device. Also among the difficulties presented with the dry bath devices is that the optical cuvet may become scratched along insertion and/or removal from the heater socket. This is highly undesirable because small scratches will scatter light when the cuvet is placed in a spectrophotometer in subsequent optical tests. Notwithstanding these difficulties, dry bath techniques are tending to replace the wet bath techniques because of the fewer manipulative steps required. This is a particularly important factor in mass blood testing procedures.
Also among the techniques which have been suggested in the prior art is to use a forced hot air type of incubator. This suffers from the difficulty that there is a severe time/temperature lag which is undesirable, particularly in mass testing environments.
It is among the general objects of the invention to provide a blood incubation device which overcomes the difficulties presented by the presently available systems.